In the operation of furnaces and in metallurgical processes it is often necessary to supply solids to be burned or chemically reacted to a combustion chamber or reactor in a suspension.
An apparatus of this type for producing such a suspension can be a burner and may comprise feeders which are uniformly arranged one in the other and are partly stationary and partly movable and initially produce a mixture of fuel and primary air and then mix that mixture with secondary air (German Pat. No. 891,597).
In order to effect, inter alia, a thorough mixing of pulverized coal and air, one embodiment of that apparatus comprises an insert, which is disposed in the primary air tube and imparts a swirl to the primary air before the pulverized coal is added so that the addition of the pulverized coal results in a swirling pulverized coal-air suspension owing to the swirling air. But because the subsequently added pulverized coal has a much greater mass than the air, the swirl of the latter is highly reduced or almost entirely eliminated upon such introduction so that the desired thorough mixing of all components is not effected.
German patent publication DE-AS No. 12 92 631 discloses apparatus for mixing solid particles in a gaseous entraining fluid. That apparatus comprises a swirling chamber, which has in cross-section the contour of a logarithmic spiral and has an inlet opening that is larger than its outlet opening. The supply line for the solids is coaxial to the pole and extends through the inlet opening and terminates approximately in the cross-sectional plane of the outlet opening. This apparatus in operation has the disadvantage that the solids enter the combustion or reaction chamber in a direction having a large vertical component and contact the wall defining said chamber before the reaction has been completed.
German patent publication DE-AS No. 22 53 074 discloses a process for the pyrometallurgical treatment of fine-grained solids at a temperature at which the solids are molten. In this process, a cyclone chamber is used and said solids are treated with high-oxygen gases and optional energy carriers. Sulfide ores and sulfide ore concentrates of non-ferrous metals are mixed with high-oxygen gases and optional energy carriers at a temperature below the reaction temperature to form a suspension, which at a velocity that is sufficient to prevent backfiring is charged into a vertical combustion passage and is reacted there. The resulting suspension contains mainly molten particles and is supplied to the cyclone chamber.
Laid-open German application DE-OS No. 32 12 100 discloses apparatus for a metallurgical treatment of non-ferrous metal ore concentrates, particularly sulfide ore concentrates. That apparatus comprises a generally vertically extending lance, which is provided with means for mixing gas and solids and with an accelerating nozzle, which is surrounded by an annular burner nozzle. The burner nozzle is provided with means for feeding the mixture of fuel and igniting material. In this apparatus a small nozzle is used to direct a heterogeneous mixture of solids, molten material and gas onto molten material contained in a hearth furnace. The residence times of the solids in the jet are extremely short so that the jet of particles which have not been completely reacted initiates a violent reaction in the bath and gives rise to a high turbulence in the bath. The apparatus has the disadvantage that the gas-solids suspension cannot be adequately mixed and that the solid particles remain in the gas jet only for a very short time so that the known apparatus can be operated only in reactors which contain molten baths.